Processes for the hydrogenation of organic compounds including those having functional groups have been widely practiced. Amination of alcohols, hydrogenation of nitrites to amines, hydrogenation of nitro groups as in the conversion of nitroaromatics to aromatic amines are commonplace industrial reactions. Catalysts used for the industrial hydrogenation of these compounds typically are based upon Group VIII metals. However, cobalt and nickel often are the primary metals employed. Promoter metals have been added to these catalytic metals to alter reactivity, byproduct formation and the like.
Representative patents and articles illustrating hydrogenation processes and the catalytic metals used therefor are as follows:
U.S. Pat. No. 3,127,356 discloses an improved process for preparing catalysts for the hydrogenation of organic compounds such as organic nitro compounds. Platinum, palladium or nickel is deposited on an inert support, and then, an oleophilic carbon is added to the system. Subsequently the metal is reduced to an activated state. Activating components, e.g., oxides of iron, nickel magnesium, manganese, chromium, vanadium, and tungsten may be added at various stages.
U.S. Pat. No. 4,792,626 discloses a process for the hydrogenation of dinitrotoluene to toluenediamine in the presence of a modified Raney nickel catalyst. The Raney catalyst is the product of an alkali treatment of an alloy of from 50-95 wt % aluminum and 4-45 wt % nickel or cobalt. These metals are modified with metals from the 1st, 4th, 5th, 6th, 7th and 8th subgroups of the periodic table. Iron, ruthenium, chromium, molybdenum, tungsten, niobium, tantalum, vanadium, titanium, copper, zirconium and hafnium are preferred. A small proportion of carbon monoxide is added to the reaction to prevent formation of N-alkyl toluenediamine.
Boccuzzi, F., Guglielminotti, E; Pinna, F., Signoretto, M.; Surface Composition of Pd—Fe Catalysts supported on Silica, J. Chem. Soc., Faraday Trans. (1995), 91 (18), 3237-44, disclose the formation of highly dispersed Pd—Fe bimetallic aggregates as catalysts for hydrogenation reactions.
U.S. Pat. No. 3,935,264 discloses the hydrogenation of dinitrotoluene (DNT) to toluenediamine (TDA) in the presence of an aliphatic alcohol. Preferred catalytic metals include nickel, platinum, palladium and mixtures. Raney nickel is the preferred catalytic metal. Carbon monoxide addition is found to be effective in minimizing the formation of N-alkyl toluenediamine type byproducts in the catalytic hydrogenation of DNT.
U.S. Pat. No. 6,005,143 discloses the hydrogenation of dinitrotoluene in a monolith catalytic reactor. The catalytic metal employed in the monolith catalytic reactor is a Pd/Ni bimetallic. In these catalysts, the metal loading is about 10% nickel and 1% palladium.
U.S. Pat. No. 4,743,577 discloses metallic catalysts for hydrogenation and decarbonylation reactions. The catalytic metals are based upon a porous, sintered support and a catalytic metal. Catalytic metals are dispersed upon the support in thin layers or electroplated from a salt solution. Catalyst metals are selected from among palladium, nickel, rhodium, platinum, copper, ruthenium, cobalt and mixtures.
U.S. Pat. No. 5,296,631 discloses a process for producing N-alkyl-N-methyl amines wherein a higher alcohol is reacted with methylamine. The catalyst employed is either one comprised of copper, zinc and ruthenium or one comprised of copper, zinc and palladium.
JP S47-91069 discloses the liquid phase hydrogenation of nitrites to amines using a catalyst comprised of nickel and palladium carried on an alumina support. Pd/Ni ratios range from about 0.1 to about 0.8. The proportion of primary amine is related to the level of palladium in the catalyst.
JP HEI 11-47597 discloses a hydrogenation catalyst employing a porous lithium aluminate possessing spinel as a support. A wide range of catalytic metals are suggested which include ruthenium, rhodium, silver, palladium carried on the support. Divalent metals such as magnesium zinc, cobalt nickel and copper are suggested as an additive.
Some of the problems associated with prior art palladium promoted nickel hydrogenation catalysts, i.e., Pd/Ni bimetallic catalysts, include that of relatively low selectivity and deactivation. Deactivation can be caused by a sintering of the metal and/or fouling caused by undesirable byproduct formation. Ring hydrogenated products (lights) and oligomer products (heavies) are believed to be the common byproducts causing fouling of the catalysts.